That sequence is the practical meaning of Manual J, Manual S, and Manual D. Manual J reconstructs what each room gains and loses. Manual S evaluates the exact heat pump or furnace/AC combination. Manual D determines whether newly routed supply and return ducts can deliver the room airflow before ceilings are closed. A retrofit succeeds when all three documents describe the same building.

Do not turn a Cleveland heating number into AC tonnage

Cleveland’s 1991–2020 NOAA station normals help explain why heating can dominate the equipment conversation. January’s normal maximum is 35.8°F and the normal minimum is 22.3°F; July’s values are 83.7°F and 65.3°F. Normal July precipitation is 3.67 inches. These are monthly climate summaries, not approved Manual J design temperatures or equipment capacities.

They are retained as climate context, not inserted into the retrofit calculation. The designer must identify the approved weather source used for the building and should not blend that source with normals or record extremes.

The winter and summer calculations respond differently to the building. Air leakage can strongly influence the heating load. Summer room peaks depend on roof and window exposure, internal gains, and moisture as well as conduction. Using the larger winter number to choose cooling capacity confuses load types and ignores how a heat pump’s output changes by operating condition.

A dual-fuel or furnace-plus-AC option does not eliminate this separation. The furnace is selected against the heating requirements and its own constraints; the air conditioner is checked against sensible and latent cooling. A heat pump combines functions in one refrigeration system, but Manual S still tests the heating and cooling sides independently. Nominal size is not permission to skip either test.

Retrofit inputs the old boiler cannot reveal

A boiler nameplate may reflect input rather than delivered capacity, and an older system may have been oversized. Fuel use can inform a careful analysis, but it does not replace room-by-room Manual J. The new calculation records masonry and framed assemblies, verified insulation, window performance, infiltration, roof boundaries, people, appliances, and the intended indoor conditions.

Mixed replacement windows require separate entries when their properties differ. A blanket “new windows” credit can understate loss through remaining original units, while assuming every opening is original can inflate the result. Likewise, brick appearance does not reveal the full wall assembly. The report should distinguish observed facts, documented specifications, and conservative assumptions.

The approved design-weather source must be current and stated in the load report. Neither the monthly normal nor a record low belongs in that field. If air sealing or insulation is part of the conversion, model the contracted post-improvement condition and keep a scenario for the existing condition if it helps decision-making. Selecting first and improving later can leave excess capacity.

A hypothetical brick home gaining its first ducts

For illustration, consider a hypothetical 1,650-square-foot 1920s brick two-story in Cleveland. Radiators provide heat, no central ducts exist, and replacement windows are of mixed ages. The concept places a trunk in the attic with drops to the second floor while the owner compares a ducted heat pump against a furnace-plus-AC system. This is not a statement about all Cleveland buildings and no field load is implied.

Room calculations may show that second-floor spaces have meaningful summer roof and solar gains even when the whole-house cooling total is modest beside the heating load. The proposed attic route adds another variable: ducts outside conditioned space can gain heat, leak, and require insulation. Padding equipment capacity to cover an undefined duct problem would hide the design decision rather than solve it.

The first-floor return and supply routes also need a realistic path. Chases, closets, soffits, or limited framing openings impose fitting losses and space constraints. A layout that looks possible on a diagram may not preserve structural, fire, acoustic, or code requirements. Coordination should happen before finishes are disturbed, not after the equipment order fixes an airflow demand.

Choose the equipment at both operating conditions

Manual S compares the exact matched system with the completed loads. A ducted heat pump needs manufacturer data at the approved winter condition, an auxiliary-heat strategy, and cooling data at the selected summer conditions. A furnace-and-AC combination needs the appropriate furnace output and cooling performance with the proposed coil and blower. Product-family brochures are too broad for this work.

Cold-condition heating capacity

Heat-pump output and efficiency generally change as outdoor temperature falls. The selection record should show the compressor’s available output at relevant conditions, define how supplemental heat is staged, and explain the control approach. It may be reasonable for auxiliary heat to serve some hours; the point is to make that consequence explicit without enlarging cooling capacity by default.

Summer sensible and latent performance

The cooling side uses total and sensible capacity at the proposed airflow. Cleveland’s summer moisture component cannot be erased, but it must be calculated from approved indoor/outdoor conditions, infiltration, ventilation, and internal sources—not inferred from rainfall alone. Minimum cooling output matters too, particularly when the selected heat pump has been driven upward by winter considerations.

A late equipment substitution can change coil performance, blower options, and modulation limits. The Manual S comparison therefore belongs to the exact indoor/outdoor pairing. If one component changes, the selection and distribution checks should be reopened rather than treated as interchangeable.

Design the new distribution before closing ceilings

Manual D begins with the room sensible loads and the chosen blower data. It assigns airflow targets, accounts for the effective length of fittings, and budgets pressure across the filter, coil, supply, return, registers, and grilles. The calculation should use the intended final filter, because an unplanned pressure drop can undermine the new system from its first day.

Attic ducts require an explicit sealing and insulation scope. DOE building-science guidance treats ducts outside conditioned space as a source of leakage and conductive loss that should be controlled, not disguised with larger equipment. Return leakage in an attic can also add unwanted heat and contaminants. The load assumptions, duct specifications, and construction contract must agree about the final condition.

Before ceilings and chases are closed, verify that each path can be installed as drawn and that bedrooms retain return airflow when doors are shut. Startup should document blower settings, total external static pressure, temperature behavior, and accepted airflow or balancing results. Commissioning cannot correct a fundamentally undersized chase, so field verification starts during layout.

Three documents a retrofit quote should include

The first document is the Manual J report with room loads, design-weather source, envelope inputs, and clearly marked assumptions. The second is the Manual S record for the exact matched equipment, showing both cold-weather heating behavior and summer sensible/latent performance. The third is the Manual D plan with supply and return routes, target airflows, pressure budget, and commissioning requirements.

Cleveland’s HVAC permit page identifies local permit responsibilities for heating, refrigeration, and ductwork. That page establishes administrative scope; it does not validate these three engineering documents. The proposal should address permit and inspection requirements while retaining a separate technical record.

The Ohio AC sizing guide supplies wider state context, and the 1,700-square-foot sizing guide can frame why floor area is not a selection. A Cleveland conversion must still solve its masonry, window, infiltration, attic-duct, and room-delivery facts.

The correct system is not simply the machine that replaces the boiler. It is the combination that passes separate winter and summer performance checks and fits a distribution plan that can actually be built. Keeping those decisions distinct prevents a heating-dominant climate from producing an unnecessarily large cooling system.

Sources

• NOAA/NCEI Cleveland 1991–2020 monthly normals
• City of Cleveland HVAC permits
• ACCA Manual J
• ACCA Manual S
• ACCA Manual D
• DOE cold-climate heat-pump sizing
• DOE guidance for sealed and insulated ducts